操作系统 抖动（Operating system jitter）.docVIP

操作系统 抖动（Operating system jitter） 15 what is jitter? What are the causes of the jitter A. Thrashing refers to the need to pull a page from memory when there is no free space in memory and a page break occurs - in the swap area of the data feed disk, if the algorithm is not appropriate, the newly changed page is quickly accessed and needs to be redeployed, so a page should be selected - the page that is being replaced will soon be accessed again, so it will need to be transferred to the page so frequently that it will cost a lot of money - time, we call this phenomenon jitter; B. The reason for the jitter is that due to the CPU utilization and the conflicting and unified contradiction between the multi-channel programming degree, in order to improve CPU utilization, - - increases multichannel programming, but simply increasing the multiprogramming degree causes a sharp rise in the page rate, which causes CPU utilization to drop The scheduling process of the system will continue to improve the multiprogramming degree to improve the CPU utilization, and the vicious cycle will be formed, which we will call the process Its in a jitter state. What is a virtual appliance? What are the key technologies that the implementation relies on? Through the virtual technology can be a Taiwanese independence of equipment transform into logical devices, for a number of users (process) used at the same time, usually called the after dealing with the virtual technology of the equipment virtual devices. The key technology that its implementation relies on is SPOOLING technology. 7. The introduction of buffer The main reasons for the introduction of the buffer mechanism of operating system can be summarized as following: (1) the contradiction between reducing the speed mismatch between CPU and I/O devices; (2) reduce the interruption frequency of cpus and relax the restriction on interrupt response time; (3) improve the parallelism between CPU and I/O devices. Features of SPOLLing system: